Analytical element and method of use

Abstract

An analytical element comprising a light-transmissive and liquid-impervious support, at least one reagent layer containing at least one reagent which reacts with a component in a fluid sample and at least one development layer provided at a position on the reagent layer on the opposite side to that of the support for permitting the component in said fluid sample to permeate into the reagent layer, at least one layer of reagent layers being constituted of polymeric particulate units each having a core-shell multi-layer structure comprising a core, which is hydrophobic and substantially unswellable with a fluid sample, and a hydrophilic outer shell.

We claim: 
     
       1. An analytical element, comprising a light-transmissive and liquid-impervious support, at least one reagent layer containing at least one reagent which reacts with a component in a fluid sample and at least one development layer provided at a position on said at least one reagent layer on the opposite side to that of said support for permitting the component in said fluid sample to permeate into said at least one reagent layer, wherein at least one reagent layer of said at least one reagent layers is composed of polymeric particulate units each having a core-shell multilayer structure comprising a hydrophobic core, which is substantially non-swellable when in contact with a fluid sample, and a hydrophilic outer shell, wherein the polymeric particulate units are bound to adjacent polymeric particulate units by mutual adhesion of the respective hydrophilic outer shells, said polymeric particulate units forming voids which substantially impede the development of a fluid sample in the lateral direction. 
     
     
       2. The analytical element of claim 1, wherein said polymeric particulate units consist of about 90 to about 0.05% by weight of the hydrophilic outer shell and about 99.95 to about 10% by weight of the hydrophobic core. 
     
     
       3. The analytical element of claim 1, wherein said polymeric particulate units consist of about 25 to about 0.5% by weight of the hydrophilic outer shell and about 99.5 to about 75% by weight of the hydrophobic core. 
     
     
       4. The analytical element of claim 1, wherein said hydrophobic core has a degree of swelling of less than about 20%. 
     
     
       5. The analytical element of claim 1, wherein said core consists of a polymer of at least one monomer selected from the group consisting of styrenes, acrylates, methacrylates, acrylonitriles, methacrylonitriles, vinyl halides, vinylene halides, conjugated dienes, crosslinking monomers, and monomers having non-radical polymerizable functional groups. 
     
     
       6. The analytical element of claim 1, wherein said outer shell consists of at least one water-soluble polymer selected from the group consisting of gelatins, water-soluble celluloses, pullulanes, and water-soluble vinyl polymers, or a polymer of at least one water-soluble monomer selected from the group consisting of vinyl acid amides and vinyl heterocyclic compounds. 
     
     
       7. The analytical element of claim 1, wherein said polymeric particulate units have a size of from about 0.1 to about 200 microns. 
     
     
       8. The analytical element of claim 7, wherein said polymeric particulate units have a size of from about 0.3 to about 100 microns. 
     
     
       9. The analytical element of claim 7, wherein said reagent layer has a voids volume of from about 20 to about 85%. 
     
     
       10. An analytical element, comprising a light-transmissive and liquid-impervious support, at least one reagent layer containing at least one reagent which reacts with a component in a fluid sample and at least one development layer provided at a position on said at least one reagent layer on the opposite side to that of said support for permitting the component in said fluid sample to permeate into said at least one reagent layer, wherein at least one reagent layer of said at least one reagent layers is composed of polymeric particulate units having a size of from 0.1 to 200 microns, said polymeric particulate units having a core-shell multi-layer structure comprising a hydrophobic core having a degree of swelling of less than 20% which is substantially non-swellable when in contact with a fluid sample, and a hydrophilic outer shell, said core-shell being in an amount of about 25 to about 0.5% by weight and said outer shell being in an amount of about 99.5 to about 75% by weight based on the weight of said polymeric particulate units, wherein the polymeric particulate units are bound to adjacent polymeric particulate units by mutual adhesion of the respective hydrophilic outer shells, said polymeric particulate units forming voids which substantially impede the development of a fluid sample in the lateral direction. 
     
     
       11. The analytical element of claim 10, wherein said polymeric particulate units have a size of from about 0.3 to about 100 microns. 
     
     
       12. The analytical element of claim 10, wherein said reagent layer has a voids volume of from about 20 to 85%. 
     
     
       13. The analytical element of claim 10, wherein said core consists of a polymer of at least one monomer selected from the group consisting of styrenes, acrylates, methacrylates, acrylonitriles, methacrylonitriles, vinyl halides, vinylene halides, conjugated dienes, crosslinking monomers, and monomers having non-radical polymerizable functional groups. 
     
     
       14. The analytical element of claim 10, wherein said outer shell consists of at least one water-soluble polymer, selected from the group consisting of gelatins, water-soluble celluloses, pullulanes, and water-soluble vinyl polymers, or a polymer of at least one water-soluble monomer selected from the group consisting of vinyl acid amides and vinyl heterocyclic compounds. 
     
     
       15. A method of detecting the presence of a component in a biological fluid suspected of containing said component, said method comprising: contacting said fluid with an analytical element comprising a light-transmissive and liquid-impervious support, at least one reagent layer containing at least one reagent which reacts with said component in said fluid and at least one development layer provided at a position on said at least one reagent layer on the opposite side to that of said support for permitting said component in said fluid to permeate into said at least one reagent layer, wherein at least one reagent layer of said at least one reagent layer is composed of polymeric particulate units, each having a core-shell multi-layer structure comprising a hydrophobic core which is substantially non-swellable when in contact with said fluid, and a hydrophilic outer shell, wherein the polymeric particulate units are bound to adjacent polymeric particulate units by mutual adhesion of the respective hydrophilic outer shells, said polymeric particulate units forming voids which substantially impede the development of a fluid sample in the lateral direction; and   determining the effect of said component on said reagent in said at least one reagent layer.   
     
     
       16. The method of claim 15 wherein the step of determining the effect of said component on said reagent comprises determining the change in the absorption or emission of electromagnetic radiation of said reagent.